The companies have entered into a binding implementation agreement which sets out the commercial terms of a proposed merger, by amalgamation under British Virgin Islands law.
Alongside the merger, a fundraise is planned, with a minimum of £5mln being sought.
Proceeds will be earmarked for an exploration campaign aimed at the Rukwa project, in Tanzania, which is host to some 21 prospects and 4 leads with prospective resource estimates to date pencilled in at 138bn cubic feet.
It is anticipated that the merged company will join the AIM market on December 3, with well-drilling planned for the first or second quarter.
Helium One envisages the drilling of three exploration wells at Rukwa, with further drilling possibilities available subject to results in the initial wells.
“Not only is Helium One one of the few companies with a globally significant resource seeking to address the current helium supply crisis, it could also become the only company on AIM where investors can get involved with the exciting and expanding helium space.”
Attis chairman Paolo Amoruso added: "This potential transaction is excellent news for the shareholders of Attis.
“With helium wholesale prices doubling over the last two years based on critical under-supply, listed primary helium companies in Canada and Australia have experienced significant share-price appreciation over the last six months."
The merger terms, which imply a price of 2.84p per Helium One share, value Scirocco’s stake in the company at £605,000.
In a separate statement, Scirocco chief executive Tom Reynolds commented: “This is a positive development that validates Helium One's story and provides it with a platform from which it can deliver material growth.
“The valuation read across highlights the challenging market conditions at this time, but in our view, it's far more important that we now have exposure to a very exciting story with a listing on a recognised exchange.
“The exceptionally strong performance of other listed helium companies around the world in recent times gives us confidence in the value creation that Helium One can deliver following this listing, especially with such meaningful catalysts on the near-term horizon.
“As a long-term shareholder in Helium One, we wholly support this development and look forward to conclusion of the process."